A variety of plant hemagglutinins (lectins) have been shown to be an effective tool in detecting changes in membrane structure induced in a variety of cell lines. The transformation of cells by oncogenic viruses is associated with dramatic changes in the surface of the membrane. The new receptor sites exposed by (or associated with) infection and transformation by oncogenic viruses can be examined by their ability to agglutinate in the presence of lectins. Normal, non- neoplastic cell lines, are much more resistant to agglutination although they can be made susceptible by mild proteolytic treatment. The relationship of changes in membrane structure in neoplastic cell lines to other bioochemical effects associated wit cancer is a subject for intensive study in many laboratories. This work proposes to study the toxic prtein, ricin, from castor beans which has been used as a tool for examining diffeences between normal and neoplastic cells. Certain aspects about its mechanism of action (inhibition of protein synthesis), toxicity, specificity and structure will be investigated.